Removing old sliding patio door lock and handle assembly

[BigAl2]

I want to remove the old lock and handle, and replace it with a P25 lock and handle from Handlestore.com.
Can anyone tell me how to make sure the lock doesn't drop down inside the white door frame when I unscrew it please?

 

[crank39]

Hold on to the hook.........or am I missing something?

 

[BigAl2]

Thanks for replying, but is it as easy as that? That was why I was asking the question.